What questions are scientists asking about the existence of intelligent extraterrestial life? Alan Boyle talks with Seth Shostak – Senior Astronomer and Director of the Center for SETI – and Don Lincoln –physicist at Fermilab, member of the science team for the Compact Muon Solenoid at the Large Hadron Collider.

None of them are biologists.

I guess it might be interesting, sorta kinda. I’m just a little bit exasperated with physicists getting together and babbling about alien life, with only the barest, faintest understanding of biology between them. Maybe they should talk about the existence of extraterrestrial compact muon solenoids? Or better yet, maybe I should talk about it! I haven’t the slightest idea what it is!

(In case you’re new here, I have serious doubts about the existence of intelligent extraterrestrial life anywhere near us — life, sure, but our kind of intelligence represents a very tiny niche. So Shostak is just wasting everyone’s time, and physicists always overestimate the likelihood of technological civilizations.)

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Didn’t Carl Sagan bill himself as an exo- or astro-biologist? What relevance would terrestrial biology have toward alien life, anyway? I think the best conjectural image of alien intelligence was Stanislaw Lem’s Solaris.

The OP failed to credit the name of the radio program – Blog Talk Radio is only the hosting network – the show is called Virtually Speaking and is produced and run by Jay Ackroyd. The show is simulcast live via the Second Life virtual reality metaverse. In fact, PZ was a guest on this show many years ago (’07 or ’08). Please check out the show. Alana Boyle is very good and you can call in and ask questions via an 800 number.

A friend of mine is writing a book on the moon. On the issue of building colonies on the moon, he asked engineers. He didn’t talk to any biologists before he started enthusing about the plants we’ll grow in our windowsills on the moon and so forth. If engineers tell him they can build on the moon, no problem. Nothing else is needed. (I suggested he consult some scientists before he finished the book; that was his consultation).

An astronomer-biologist pairing I wouldn’t object to, since ‘what places can we have planets or moons suitable for life’ is a good question, and a biologist might not think about things like ‘Europa has an underground (under-ice?) ocean with a certain salinity and temperature and so on…’, any more than an astronomer knows the details of chemosynthesis to have life without sunlight in that under-ice ocean.

In case you’re new here, I have serious doubts about the existence of intelligent extraterrestrial life anywhere near us — life, sure, but our kind of intelligence represents a very tiny niche.

I’m curious what you mean by near. Without having any meaningful way to assign probabilities, it still doesn’t seem reasonable that we could be alone in the universe. I.e., any non-zero probability of life would have to be exactly right to have the likely outcome of exactly one instance.

On the other hand, without numbers, you cannot rule out being alone in the galaxy. It has also occurred to me that given a multiverse or some kind of recurring big bang with slightly different conditions each time, you can’t rule out being alone in what we consider to be the universe. Maybe there are many comparable domains, most of which are empty.

It would certainly be more interesting not to be alone. And maybe it’s just my optimism that makes me consider this likely. I would consider “near” to include something like the nearest thousand stars to us. It still wouldn’t make travel feasible, but some communication might occur. I don’t have an opinion on this either way, though it would be cool.

Also curious what you think a typical extraterrestrial biosphere would be like. Microbial? Multicellular but with relatively simple behavior?

I’m not sure it’s much of a step from any vertebrate brain to a human brain, and an octopus is also quite intelligent (whatever we mean by this) but must have evolved independently from a common ancestor that would be considered far less intelligent than either an octopus or a comparably intelligent vertebrate.

My gut feeling (as neither a physicist nor a biologist) is that abiogenesis may be the least probable step, and once there are multicellular organisms with sexual reproduction, the various niches are going to expand to so fast that some form of intelligence is very likely. Possibly some kind of ecological disaster occurs first, but I’m not sure if I believe that a steady-state of non-intelligent life is a likely outcome.

SETI used to have a page that pointed out how far off a 2000-meter wide radio telescope could pick up a signal. The type of stuff we usually think of as the “expanding bubble” of human emissions – television signals, radio, etc – wasn’t detectable much beyond the edge of our solar system, much less from around another star. The only type of signal we would pick up at a distance would be if an alien civilization was deliberately pinging other stars with their equivalent to the Arecibo telescope.

A friend of mine is writing a book on the moon. On the issue of building colonies on the moon, he asked engineers. He didn’t talk to any biologists before he started enthusing about the plants we’ll grow in our windowsills on the moon and so forth. I

I’m not sure what the biologists would tell him if he asked, since we don’t know how well stuff grows in lunar-level gravity. We know it can grow in microgravity (since they’ve grown plants on the ISS), but not low gravity.

“On the other hand, without numbers, you cannot rule out being alone in the galaxy.”

WITH numbers you cannot rule out being accompanied in the galaxy.

I thinks that’s more or less what you meant, because being alone in the galaxy would certainly qualify as exhausting the regions that might be termed “near”.

The farthest exoplanet detected is at a distance in the order of magnitude of 10 kLy, correct? A radius of 20-30 kLy includes only a reasonable fraction of the galaxy’s volume and probably a smaller fraction of the galaxy’s stars, given that we exist in a less-dense patch between the more dense “arms” in our spiral.

So, for now, let’s consider anything with d < (10 kLy)*(10^0.5). That gets you, logarithmically, half-way to the next order of magnitude and I think includes all the farthest exoplanets to date.

Will that satisfy your definition of "near", or would you prefer something like:

If the propulsion technology with the fastest potential speed we have in development lived up to its full promise, and was fitted to a generations-ship, any star or region accessible within the life expectancy of a baby born on the ship the day of departure counts as “near”.

Or, perhaps we could just be reasonable and say that since you are of the mind that an otherwise empty galaxy can’t quite be ruled out, and since getting to the next galaxy over would take a bit of doing with tech we cannot currently even envisage, we might as well not fuck around with definitions of “near” because whatever that definition is, PZ’s almost certainly right.

I’m also getting fairly tired of seeing conversations about the ethics and likely consequences of contacting aliens where all the participants are white and male. SETI should try engaging with a wider spectrum of humanity before trying its luck with something actually alien: for starters it would be many orders of magnitude easier to achieve.

Crip Dyke, Right Reverend Feminist FuckToy of Death & Her Handmaidensays

I thinks that’s more or less what you meant, because being alone in the galaxy would certainly qualify as exhausting the regions that might be termed “near”.

Sorry, I didn’t mean to suggest that was “near”. Being alone in the galaxy, or even having a neighbor halfway across the galaxy would be very alone. My point was that I don’t see any way to rule it out without a quantitative argument and I don’t have sufficient background to evaluate the numbers (for the Drake equation or something similar).

If the propulsion technology with the fastest potential speed we have in development lived up to its full promise, and was fitted to a generations-ship, any star or region accessible within the life expectancy of a baby born on the ship the day of departure counts as “near”.

I’m not that much of an optimist. Even getting close to lightspeed requires an unreasonable amount of energy. I don’t expect such a starship to be built to carry biological life. Some kind of self-replicating probe, maybe, but this might travel for thousands of years at a small fraction of lightspeed.

Something like 10k lightyears is near enough for me. Two-way communication would not exist as we know it today, but maybe some aliens would have an interest in advertising their existence, and there could be some kind of technology sharing over long time periods.

Crip Dyke, Right Reverend Feminist FuckToy of Death & Her Handmaidensays

Ah, okay. Maybe I was reading your comment aggressively or something, but i did come to the conclusion that you were asserting some one or two civs elsewhere in the galaxy would constitute having intelligent neighbors “near”.

It would certainly be more interesting not to be alone. And maybe it’s just my optimism that makes me consider this likely. I would consider “near” to include something like the nearest thousand stars to us. It still wouldn’t make travel feasible, but some communication might occur. I don’t have an opinion on this either way, though it would be cool.

That seems awfully restrictive to me. We also don’t have to be so arbitrary and parochial about it, by picking the closest thousand stars or something like that. We know that, if we were even going to begin to look at the very big picture with its long times and large distances, everything except our local cluster (i.e., Milky Way, Andromeda, dwarf galaxies nearby, etc.) will all expand away from us. So we don’t exactly need to toss all of the rest out, because the universe does the tossing for us. Very easy. The idea is that no matter what technology you dream up and how much time you wait, we can very safely figure that, practically speaking, everything outside of that is utterly out of reach. So forget about asking for evidence of life there (or no life being there). We won’t ever shake hands or conduct wars or become pen pals or anything like that, with something that came from outside, if there are such things. It’s not happening, not now or tomorrow or in a trillion years. So, practically speaking, there’s no reason for anyone to ever call anything beyond that “near” us, in the sense that matters in a conversation like this.

Of course, you could care about something else and have a different conversation, not about the existence (throughout the universe) of life or what kind of evidence we’ll find for that. That other sense of being “near” us generally means they’d have to be much, much closer than what you’re suggesting. That is, people care about answering other kinds of questions too. Were you abducted by intelligent aliens last night when you walked out of the bar? No, there aren’t any “near” us, and you were probably just drunk. If they were that close, you would not have been getting your evidence for it from a thousand light years away or whatever. They deliver it to you, obviously. Or another question: did some non-intelligent alien microorganism infect you with its alien toxins, which is why you have that weird rash? No, there’s no evidence of anything like that being “near” us either. Anyway, it wouldn’t help to have some arbitrary number to do all of the work, since it’s not a real physical distinction and since it might also bias the answers we give.

My gut feeling (as neither a physicist nor a biologist) is that abiogenesis may be the least probable step, and once there are multicellular organisms with sexual reproduction, the various niches are going to expand to so fast that some form of intelligence is very likely. Possibly some kind of ecological disaster occurs first, but I’m not sure if I believe that a steady-state of non-intelligent life is a likely outcome.

I thought you were saying such probabilities were ill-defined… The probability of abiogenesis is one, which is not low or less than any other probability of anything. We know it happened in the past. (If life emerged somewhere other than Earth and traveled here, that still counts as abiogenesis for our purposes.) I mean, who is supposed to be rolling which dice that makes it improbable at all? Maybe I’m just ignorant though — is there some other mechanism that’s on the table, that we could say also has a chance of being true? Of course, “God did it” is not what I consider a mechanism, but that is an idea that people have. Other than things like that or being a brain in a vat or living in the Matrix or whatever, why wouldn’t we say the probability is one?

That other sense of being “near” us generally means they’d have to be much, much closer than what you’re suggesting. That is, people care about answering other kinds of questions too. Were you abducted by intelligent aliens last night when you walked out of the bar? No, there aren’t any “near” us, and you were probably just drunk.

That’s why I was asking what PZ meant. I think “near” could mean a lot of different things and the implications would also be very different. Maybe it’s the wrong question to ask. A better question is whether we will be able to confirm the existence of intelligent life in the foreseeable future (or within my own lifetime, to personalize it).

BTW, I agree that the nearest 1000 stars is totally arbitrary. But I am trying to attaching something concrete to the notion of “near” and it was the first thought that came to mind.

I thought you were saying such probabilities were ill-defined… The probability of abiogenesis is one, which is not low or less than any other probability of anything.

The probability of it happening on any particular planet. I doubt it’s close to 1. Most planets aren’t suitable for any kind of life as far as I know (based on this solar system). Even a planet with the same characteristics as earth (same distribution of elements, mass, distance from a sun-like star) might not do the same thing. Maybe some other reaction would happen first that made the development of self-replicating molecules very unlikely. I don’t think there is sufficient data to say.

The probabilities aren’t ill-defined, though. I just don’t know them. As I said, I have a gut-feeling about it, which is that getting life in the first place might be the least likely part. I also think that once you have a eukaryotic cell with sexual reproduction, it may be more likely than not that it leads to the development of complex and diverse lifeforms that exploit every niche including intelligence.

Biologists; give us a robust and portable test for “aliveness” please.

My Astronomy 101 students always want to do research projects on extraterrestrial life. I wave them off, on the grounds that we don’t know what the word “life” means well-enough to really look for it anyplace except for places very much like the places that we find it on the earth. I explain that when we look for warmish, wettish places — and say “maybe life?”, we mean is that maybe we will recognize an alive thing if we see it there, if it looks enough like the things we class as “alive”, and does the kinds of things “living things” mostly do.

My students sometimes get very upset and show me a list of 7 or 8 things that define “alive” according their Biology 101 instructor, and then I tell them about the mining engineers of Janus VI who mistook Horta eggs for an interesting kind of mineral deposit… which doesn’t really mean anything to kids who only know Shatner as Kaley Cuoco’s father.

Am I the only one who, upon seeing Shostak’s name, always thinks of the gostak (which distims the doshes)? I figured I was.
For some reason it seems appropriate to me. Maybe it’s because terms like “life” and “intelligence” aren’t as well defined as we could wish.

Might also be because SETI and our ability to identify exoplanets were science fiction around the time I first read Breuer’s story (in an anthology).

Everyone I’ve ever heard of talking about this subject uses probabilistic language, but the truth is, we have no quantifiable numbers to put to those probabilities whatsoever. All the meagre data we currently have can equally support the notion that intelligent life is ubiquitous in this universe, or the notion that we are completely alone.

The 95% CI is 1 to infinity.

Also, when talking about intelligent alien life, we also need to define intelligence. Is a spider intelligent? A squid? A beaver? A beehive?

I have serious doubts about the existence of intelligent extraterrestrial life anywhere near us

If unlikely outcomes are a reason to not bother trying things, then I have to wonder why you’ve committed so many resources over the years for such little net effect. I don’t remember you always being this conservative, openly mocking people for having aspirations and putting their hopes to the test instead of taking the safe route.

So Shostak is just wasting everyone’s time

Who the hell are you to decide what people should be interested in or how they spend their time? Arrogant asshole.

All the meagre data we currently have can equally support the notion that intelligent life is ubiquitous in this universe, or the notion that we are completely alone.

As I tried to point out, you don’t need specific numbers to question the reasonability that there is exactly one intelligent life form in the universe, provided that what we think of as the universe encompasses all of existence (i.e. not one part of a multiverse or some kind of series of repeating universes).

Let p be the probability of finding intelligent life around any star at any time in the history of the universe. It would vary by star, but you can even it out by saying, what is the probability of finding life on a star chosen with uniform probability at any time chosen with uniform probability?

I don’t know the value of p, but if it is sufficiently low, then there is a high probability that there are 0 stars with intelligent life (consider a hypothetical universe in which this could hold). If p is sufficiently high, there is a high probability of finding many more than one such star.

The range of p in which you would find anything but a vanishingly small probability of exactly one star with intelligent life would be so narrow that it would look like a “fine-tuning” argument. There is no particular reason to think that p would lie in such a narrow range, and therefore no reason to start with the hypothesis that we’re alone. We can also rule out 0 such stars because we have ourselves as a counterexample. The most reasonable hypothesis is that there are multiple intelligences within the total domain of existence (whether or not this is the universe as commonly understood).

The argument does not require quantities, since it considers all possible values of p between 0 and 1. It also doesn’t apply to a more practical question, like whether we’re alone in the galaxy, but it’s sufficient for me to conclude that we’re not alone in the universe (and in practice I do mean universe as commonly understood).

The range of p in which you would find anything but a vanishingly small probability of exactly one star with intelligent life would be so narrow that it would look like a “fine-tuning” argument. There is no particular reason to think that p would lie in such a narrow range, and therefore no reason to start with the hypothesis that we’re alone.

This is bizarre. I don’t get it. Suppose there’s a probability of about 50.1% for something. We get evidence, that’s what we observe it to be, and that’s how we know that. But of course you could also say something similar by specifying a range: it’s between 50.09% and 50.11%, for example. The more digits we add, as we made this even more precise given whatever we observe about what actually happens, then apparently you’re saying you should be ever more surprised by the fact that it’s within that range of values … instead of some other range. But if we’re doing this correctly, it must be in some range or another. It’s as if you’re saying it can’t be any number at all, not really, since all numbers are in some narrow, vanishingly small range. And they’re in very wide and enormously big ranges. Because they’re numbers. Who cares? Things like that will not help us at all.

We should also make a distinction between “alone” and “functionally alone”.

If the frequency of intelligent species in the universe is below a certain threshold, then individual examples of intelligence will be separated by gulfs of time and/or space so vast that it would be impossible for either of them to ever detect the other. And this is what I mean by “functionally alone”. Any frequency of intelligent life in the universe lower than this threshold becomes a question of faith and philosophy, and not science, since it is an untestable conjecture, and, for me, is really not that interesting.

#27 consciousness razor
Actually, I admit my argument doesn’t really work. I still think it is not a reasonable starting point to assume that we’re alone in the universe, even without specific quantities, though I’m not longer sure why I think that. On the other hand, it’s totally reasonable to hypothesize that we’re alone in the galaxy if the distribution of intelligent life is sufficiently sparse (though my guess is we’re not, but that’s more along the lines of wishful thinking).

One reason it’s problematic to use probabilities in this context is that there is a sample space of one universe. On the other hand, if you propose a distribution of hypothetical “universes” with different laws, different initial conditions, and different outcomes of the occurrence of intelligent life, it is not at all unreasonable to have the vast majority of them with no intelligent life at all, a small fraction with one instance, and diminishing numbers with denser distributions of intelligence. The weak anthropic principle would also limit observation to those universes with at least one instance of intelligent life, suggesting that it might actually be very reasonable to think we’re alone.

However, the above scenario would not be “alone in all of existence” just “alone in one possible universe out of many.” If the universe is taken to be equivalent to all of existence, then the above argument doesn’t apply.

There are cases in which it is reasonable to assume that something is unique among the set of things that exist (if existence is limited to the observable universe). If I start flipping coins until I have a series of 1000 random heads and tails, it is probably a series that is not duplicated elsewhere in the universe. But intelligent life is a category of things, and it seems unlikely that we would be the only instance of that category, any more than my series would be the only instance of a series of coin flips.

It did occur to me that my previous argument is bogus if you assume a single universe, because the probability p is simplify determined by the number of instances of intelligent life.

So, hmm… On the one hand, say my sequence of coin flips is unique does not give it any privileged status, but saying that human beings are the unique example of intelligent life does give humans a privileged status that seems unwarranted. I am inclined to stick by these assertions, but I actually don’t have a good justification handy.

Any frequency of intelligent life in the universe lower than this threshold becomes a question of faith and philosophy, and not science, since it is an untestable conjecture, and, for me, is really not that interesting.

I think it could also be a question of mathematics in that given a particular model of the universe and sufficient analytical understanding, you could determine the frequency of intelligent life in that model. An inability to test it empirically is a drawback, and it might be uninteresting to you, but it could still be of interest in a more abstract sense, and more rigorous than an assertion of faith.

The argument is that p must be above a threshold to allow a universe to reasonably contain 1 intelligent civ.

I don’t understand. There’s no “threshold”, there’s nothing “allowing” a universe to do anything, and nothing that “must be” because of it.

The probability Paul BC was talking about reflects what you observe (if we had any observations like this to begin with) to be the case. There is some number of stars or some volume of space. You count, to find the proportion which contains life, intelligent life, cheese, unicorns, snowflakes with exactly 10^29 atoms, or whatever it may be that you’re interested in finding. Maybe, in the process, you don’t find any. But that’s a number, based on what you found, which represents an idea you have about what you found.

So, suppose you have one trillion cubic parsecs, or whatever it is. Within that you find only one intelligent civilization, so you get this sort of ratio: 1 intelligent civilization / trillion cubic parsecs

Of course, that’s not a probability. It’s a proportion of two quantities, which could be counting anything. We could write down things like (Gallons of Milk)/sec^2 and it would not be giving us what we’re actually looking for in a probability, even if it could be normalized and so on. Because you have to understand physically what’s at stake, not just toss numbers around aimlessly.

If the universe has an infinite amount of space, for example, then this entire exercise is not just pointless (because the answer is trivial) but the procedure being discussed is not even mathematically coherent. We had better find a different way of determining what’s likely and what isn’t, if that’s what we wanted to do. But I figure this would be a silly way to do it no matter what, since we have good reasons to believe life, as an actual physical phenomenon that’s already been studied in great detail on this planet, doesn’t need to appear just by fluctuating out of the void. It can and does actually occur by specific physical/chemical processes that you would have to analyze very closely, in order to determine the probabilities of those events in environments where events like that can take place.

Anyway, uniformly chopping up all of spacetime for this is not helpful. Pretty much the only thing you’re going to find that way which has a not-stupendously-tiny “probability” is the vacuum of space. But we don’t actually think asteroids or clouds of dust are “unlikely” simply because they don’t fill up every dimension to a certain ratio. Even if you felt like making such a measurement, it just would not make sense to call that thing a probability.

Also, there’s nothing about what it “must” be or what “allows” it to be so, even if we had any actual probability to work with (which we most certainly don’t) as compared to a gut feeling based on no data at all. If we had an actual probability, you can’t derive things like that from them.

But I figure this would be a silly way to do it no matter what, since we have good reasons to believe life, as an actual physical phenomenon that’s already been studied in great detail on this planet, doesn’t need to appear just by fluctuating out of the void.

I also admit that the fact that there are plausible mechanisms to explain how we got from inanimate matter to intelligent life on earth is a stronger basis than any abstract argument for believing there is other intelligent life in the universe. We’re probably a lot closer than decades ago to getting a sense of the frequency of earthlike exoplanets through direct observation and it seems reasonable to hypothesize similar processes happening on such planets at least some of the time.

As much as I would like to believe in live some where else in the universe. I really would it is only recently that we have made verifiable observations of other planet systems
I have listen to none biologists talk about life on other planets and am always disappointed. There is always a lot of enthusiasm and positive feelings and excitement but little else
unless someone invents the warp drive and the Ansible it is all pipe dreams and in danger of becoming another heaven a mythical destination we can not reach
keep looking it is fine but we have real places to go to right here closer that have many secrets waiting to be found.
But let the experts in their fields speak about what they know best about please
uncle frogy

From what I can tell from the reviews I’ve read, the Medea Hypothesis does NOT assume microbial intelligence. I have no idea how seriously to take Ward’s idea because I don’t feel like sitting through his TED talk or buying his book and the reviews linked to on Wikipedia were just plain awful (as in, they were written by people who didn’t give an informed opinion on the quality of his arguments), so at the moment I’m putting it in the mental drawer marked “Probably wrong” rather than “Pseudoscience”. I’m happy to be persuaded otherwise if you have some specific examples from his work that fit the label.

Oh, I think there is plenty of exobacteria out there.
The shores of the exooceans will have plenty of exostromatolites.
On land -if you are lucky- you might be able to see fruiting bodies of slime mould.
Even lichen* are rather advanced organisms compared to what we are likely to find in most places.
.
Multicellular life (judging by a sample of one) required oxygen rising to at least1% of the air. Also, a carbon cycle driven by tectonic activity is nice.
* Yes, I know lichen are two organisms working together.

We have very large-brained beings on this planet with whom we cannot communicate, even though we know they have a vast and elaborate network of highly abstract signaling on which we can freely eavesdrop, a social structure that shows complex patterns of cooperation, and a somewhat-familiar anatomy and physiology.

But since these organisms have no technology and no chance of developing one, we instead destroy their habitat and hunt many of those which survive for food for ourselves and our pets (and, for several centuries, for our lamps).

Astronomers can tell us about all the incredible places out there that have been discovered over the last decades that might harbor self-replicating systems. Biologists can tell us about… erm… nothing extraterrestrial at all. Meaning no offense, PZ, but as long as extraterrestrial life is pure speculation, and anything we know on Earth may be totally different from it, I find it more interesting to listen to people who actually observe other worlds.

We have very large-brained beings on this planet with whom we cannot communicate, even though we know they have a vast and elaborate network of highly abstract signaling on which we can freely eavesdrop, a social structure that shows complex patterns of cooperation, and a somewhat-familiar anatomy and physiology.

If we ever do make contact with what appears to be another intelligent civilization, and if there are any obvious indications that they are technologically more advanced than us (obvious as in, say, that’s THEIR big interstellar ship in the cornfield over there that they landed on our world to come visit us, or their broadcast signal that we received is several orders of magnitude more powerful than anything we can ourselves produce….) it may be that the most sensible thing to do is not try to figure out a way to communicate with them, but just act normally and wait to see if THEY figure out a way to communicate with us. Being more advanced, it may well be easier for them to figure out a way to initiate communication than vice versa, and if they actually made the effort to initiate contact themselves, either by travel or by messaging, then it is certainly possible that they’ve already made contingency plans for communication and it would make sense to wait and see if this is the case.

Since we only have one known life-bearing planet at this point (Earth), biologists can at least point out that a species capable of intelligence and recursive-tool-creation civilization is an extremely rare phenomena in said planet’s history. Intelligence is rare among animals, tool-using even rarer, tool- creation even rarer than that, and so forth.

Astronomers, at least at this point, can’t tell us anything other than that there’s probably a near-Earth-sized planet around this star in what is possibly its habitable zone.

My gut feeling (as neither a physicist nor a biologist) is that abiogenesis may be the least probable step, and once there are multicellular organisms with sexual reproduction, the various niches are going to expand to so fast that some form of intelligence is very likely.

Based on our sample of 1, wouldn’t it make more sense to conclude that multicellularity is the least probable step? Abiogenesis seems to have occurred remarkably quickly, ~3.6 BYA, around the end of the bombardment phase (even, as has been proposed, occurring more than once during late bombardment only to be wiped out and occur again, not that it would be possible to prove); but the first multicellular organisms didn’t evolve until ~2 BY after that, and only after biological processes produced sufficient atmospheric oxygen to support robust aerobic metabolisms.
And intelligence (defined SETI-wise as the ability to create a technological civilization) didn’t arise in any obviously inevitable way from the expansion of “various niches”, it seems hugely dependent on a whole series of evolutionary and geological contingencies, and (again, sample of 1 and all) took a good half a billion years even after the evolution of the tetrapod clade in which it arose.

Based on our sample of 1, wouldn’t it make more sense to conclude that multicellularity is the least probable step?

To be honest, I have no idea. Is there any evidence of multicellularity evolving independently? Do slime molds count? (and are they independent?)

And intelligence (defined SETI-wise as the ability to create a technological civilization) didn’t arise in any obviously inevitable way from the expansion of “various niches”

Maybe not, but I think there is evidence for the likelihood of behavioral intelligence at the level of an octopus or comparably intelligent vertebrate because their common ancestor dd not share it. I also don’t think humans are really that much smarter than, say, other mammals. They have some advantages in language and tool-making. It’s not inevitable that this would lead to proliferation (given the cost of a big brain) but seems plausible. It would also be useful to have a better understanding of the intelligence of non-primates such as whales and elephants, which also rose independently from a less intelligent ancestor.

PaulBC,
“some advantages”?! Language and tool making is everything. It’s general-purpose higher order reasoning and the ability to collectively share the results of same across time and space. No other animal has anything even close, and only our close cousins the other primates have even the glimmers of a theory of mind, a robust one of which is what gives rise to a self-model and the resultant ability to introspect and entertain counterfactuals for scenario planning.

It would also be useful to have a better understanding of the intelligence of non-primates such as whales and elephants

I agree, I’m fascinated by the subject. What I believe we do know is that human intelligence can be differentiated from other instances of intelligence by its general-purpose nature. A book you might find interesting is Wild Minds, by Marc Hauser. From it I learned that an animal’s cognitive abilities are as a general rule a limited toolkit with specialized functions that are closely tied to the particular challenges presented by the lineage’s habitat and ecology and degree of sociality. Hauser challenges the idea of any kind of linear progression from “simpler, dumber” forms of cognitive problem-solving to “more complex, more widely useful (human-like)”. Rather, different species have the cognitive tools they need to successfully navigate their environments. Duh, I know, but the book is filled with interesting examples of experimentally revealed “blind-spots” in the cognitive abilities of animals generally regarded as “smart”, showing that the ability to reason from first principles or apply a tool in the kit that is specialized for one thing to a novel circumstance is just not present in any but a very few lineages and maybe only in ours. It’s also a corrective to our tendency to isolate a few components of an animal’s cognitive abilities that give rise to behaviors we can anthropomorphize, and calling an animal “smart” or less so in proportion to how interesting we find their behavior.

No. In no universe is that even remotely alike….
A biologist could be qualified to make educated speculations on the subject (more qualified than the other members of the comittee, in fact), whereas a priest would be qualified to do fuck all in that situation.
It’s really simple…if the topic is “life”, then biologists are the people to talk to.

Human-level intelligence seems to be a “break-out” capability, when you consider what happened with us compared to our simian cousins (particularly chimps and bonobos). Some degree of animal intelligence evolved multiple times independently – in mammals, in some birds, in elephants, in some whales and dolphins, in octopi – but only one species “broke out” and developed a technological civilization.

I suppose we could just be the first, and eventually one of those species would have gone that route. But I’m not quite convinced on that – it feels chancy to me.

Huh. Not having read the book itself, I’ve never seen the Medea hypothesis put in such literal terms of conscious intent as the Wikipedia article does it. Isn’t that just another silly misunderstanding like taking “selfish gene” literally?

The name is a deliberate reaction to the Gaia hypothesis. The Gaia hypothesis, even if not taken in terms of conscious intent like Lovelock did, says that life ends up creating and maintaining the best conditions for living long & prospering. The Medea hypothesis says that no such thing is guaranteed, that instead life can cause mass extinctions and has repeatedly done so.

Also, when talking about intelligent alien life, we also need to define intelligence. Is a spider intelligent? A squid? A beaver? A beehive?

The astrophysical definition of intelligence, sensibly enough, is the ability to build a radio telescope.

So Shostak is just wasting everyone’s time

Who the hell are you to decide what people should be interested in or how they spend their time? Arrogant asshole.

What do you mean by “decide”? PZ has every right to hold the opinion that Shostak is wasting everyone’s time, and he has every right to publish it. He doesn’t need to be anyone for that.

It should also be noted that a spacefaring civilization is by no means constrained solely to habitable planets.

Indeed, an argument can be made that the kind of life capable of building radio transmitters powerful enough that we could detect them (ie a fair bit more advanced and technologically capable than we are) might even be more likely to gravitate to star system types than can’t have habitable planets rager than ones that do.

Definitely agreed on that one. In fact, I tend to believe that a spacefaring civilization would largely live in habitats, since once you’re up there in space it’s easier to get around that way – and you can tailor the conditions inside of the habitat to whatever you want, including the simulated gravity from rotating it.

It’s also why I’m not quite as negative on the “generation ship” idea as I used to be. Any civilization that sends one out likely has many years of experience of living in self-contained habitats running on either solar or nuclear power and resources gathered from external sources, and have done slow interplanetary travel already in their habitats from a combination of ion thrusters and the Interplanetary Transport Network. To them, a generation ship would just be a more extreme version of that, where you run solely on nuclear power and have to bring your own supplies so you can replace and fabricate new parts as you go.